1. Field of the Invention
This invention relates to a deposited-film formation apparatus, a deposited-film formation process, a vacuum system, a leak judgment method, and a computer-readable recording medium with a recorded program. More particularly, this invention relates to a deposited-film formation apparatus, a deposited-film formation process, a vacuum system, a leak judgment method, and a computer-readable recording medium with a recorded leak-judgment-executable program (a recording medium any information recorded in which is readable by a computer and in which a program capable of executing the judgment of a leak of air has been recorded) which apparatus, process, system, method and medium can perform detection of any inclusion of air from the outside.
2. Related Background Art
Various proposals are conventionally made on processes for making functional deposited films for solar cells such as amorphous silicon solar cells and electrophotographic photosensitive members. Such deposited films are commonly formed by means of a vacuum system, which decomposes material gases to form deposited films. In this vacuum system, entrance (or inclusion) (hereinafter often “leak”) of air from the outside must be prevented for the reasons as stated below.
One of the reasons is that the material gases which may spontaneously ignite upon self-decomposition with air are used as material gases used to form the deposited films. Hence, any air entering the vacuum system from the outside due to leak causes undesired decomposition inside a vacuum chamber of the vacuum system. The undesired decomposition is caused by self-decomposition with air. Therefore, the self-decomposition may preferably be suppressed during deposited film formation.
Incidentally, air having entered in a large quantity due to leak may cause explosion dangerously.
Another reason is that even slight leak of air (in particular, oxygen) in deposited films makes the resultant functional deposited films have greatly poor electrical properties. Hence, systems or apparatus for forming the deposited films must be provided with chambers and piping which are highly vacuum enough for the air not to enter from the outside. Also, the systems must periodically be checked so that the air do not enter from the outside.
As methods for detecting any leak to examine whether or not air has entered (leaked) the vacuum chamber or piping from the outside, the following methods are commonly used. Methods for detecting leaks are roughly grouped into a “pressure method” in which the structure to be examined is brought into a pressed condition and a “vacuum method” in which the structure to be examined is brought into a vacuum condition.
The pressure method includes a “pressure and leaving method” in which the inside of the structure to be examined is pressurized and any change in pressure after a certain time is measured with a pressure gauge, a “pressure and foaming method” in which the structure to be examined is coated with a foamable solution and any foams formed thereat are visually observed, and a “halogen leak test method” in which the structure to be examined is pressurized with a halogen gas and thereafter any gas leaking outside is detected with a halogen leak detector.
The vacuum method includes a “vacuum and leaving method” in which the inside of the structure to be examined is evacuated and any change in pressure after a certain time is measured with a vacuum gauge, a “Geissler tube method” in which after evacuation any change in color of discharge ascribable to a probe gas is visually observed, and a “helium leak test method” in which after evacuation the structure to be examined is sprayed with helium gas from the outside and any gas leaking inside is detected with a helium leak detector.
It is common to form deposited films in a state where air has been kept not entering the vacuum system while managing any of these methods. It is considered possible to form deposited films in a state free of any leak while judging the leak of air by such methods.
However, in such leak detection methods, the following problems may arise in the case of apparatus which make use of material gases in a large quantity and also are continuously operated for the purpose of mass production-of deposited films as in the case of an apparatus for forming solar cells comprised of amorphous silicon which are intended for electric power generation.
In the above leak detection methods, the apparatus must be tested in a condition different from a condition where the deposited films are being formed, e.g., the apparatus is made airtight and certain specific gases are flowed. For example, at the time of maintenance, a service person must make sure of any leak. However, even when good results are obtained on the check of leaks at a certain point of time, a leak may occur because of, e.g., looseness of flanges at a point of time where deposited films are again begun to be formed. A leak may also suddenly occur because of an earthquake or the like. Accordingly, under such situations, it is impossible to detect the leak when it occurs in the midst of formation of deposited films.
As another problem, when a deposited-film formation apparatus has a large scale, when it takes a long time to form deposited films or when material gases are used in a large quantity, the formation of deposited films may inevitably be continued as the air is kept included inside the apparatus, so that deposited films having a low quality may be produced in a large quantity. Also, the material gases used in a large quantity are spontaneously ignitable gases and, in some cases, some have a high toxicity. Hence, if the formation of deposited films is continued as the leak is left unrepaired, there is a danger of causing a fire or explosion as a result of the reaction of material gases with the air, or being exposed to gas leakage to become injured.
Under such circumstances, it is sought to make an improvement in order to form functional deposited films in a large quantity, safely and stably.